As wireless communication systems such as cellular telephone, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication subsystems transmitting a growing volume of data with a fixed resource such as a fixed channel bandwidth accommodating a fixed data packet size. Traditional communication system designs employing a fixed resource (e.g., a fixed data rate for each user) have become challenged to provide high, but flexible, data transmission rates in view of the rapidly growing customer base.
The third generation partnership project long term evolution (“3GPP LTE”) is the name generally used to describe an ongoing effort across the industry to improve the universal mobile telecommunications system (“UMTS”) for mobile communications. The improvements are being made to cope with continuing new requirements and the growing base of users. Goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards and backwards compatibility with some existing infrastructure that is compliant with earlier standards. The project envisions a packet switched communications environment with support for such services as VoIP (“Voice over Internet Protocol”). The 3GPP LTE project is not itself a standard-generating effort, but will result in new recommendations for standards for the UMTS.
The UTRAN includes multiple Radio Network Subsystems (RNSs), each of which contains at least one Radio Network Controller (RNC). However, it should be noted that the RNC may not be present in the actual implemented systems incorporating Long Term Evolution (LTE) of UTRAN (E-UTRAN). LTE may include a centralized or decentralized entity for control information. In UTRAN operation, each RNC may be connected to multiple Node Bs which are the UMTS counterparts to Global System for Mobile Communications (GSM) base stations. In E-UTRAN systems, the e-Node B may be, or is, connected directly to the access gateway (“aGW,” sometimes referred to as the services gateway “sGW”). Each Node B may be in radio contact with multiple UEs (generally, user equipment including mobile transceivers or cellphones, although other devices such as fixed cellular phones, mobile web browsers, laptops, PDAs, MP3 players, gaming devices with transceivers may also be UEs) via the radio Uu interface.
The wireless communication systems as described herein are applicable to, for instance, 3GPP LTE compatible wireless communication systems and of interest is an aspect of LTE referred to as “evolved UMTS Terrestrial Radio Access Network,” or E-UTRAN. In general, E-UTRAN resources are assigned more or less temporarily by the network to one or more UEs by use of allocation tables, or more generally by use of a downlink resource assignment channel or physical downlink control channel (PDCCH). LTE is a packet-based system and therefore, there may not be a dedicated connection reserved for communication between a UE and the network. Users are generally scheduled on a shared channel every transmission time interval (TTI) by a Node B or an evolved Node B (e-Node B). A Node B or an e-Node B controls the communications between user equipment terminals in a cell served by the Node B or e-Node B. In general, one Node B or e-Node B serves each cell. A Node B may be sometimes referred to as a “base station.” Resources needed for data transfer are assigned either as one time assignments or in a persistent/semi-static way. The LTE, also referred to as 3.9G, generally supports a large number of users per cell with quasi-instantaneous access to radio resources in the active state. It is a design requirement that at least 200 users per cell should be supported in the active state for spectrum allocations up to 5 megahertz (MHz), and at least 400 users for a higher spectrum allocation.
In order to facilitate scheduling on the shared channel, the e-Node B transmits a resource allocation to a particular UE in a downlink-shared control channel (PDCCH) to the UE. The allocation information may be related to both uplink and downlink channels. The allocation information may include information about which resource blocks in the frequency domain or time domain, or both, are allocated to the scheduled user(s), the modulation and coding schemes to use, what the size of the transport block is, and the like.
The lowest level of communication in the e-UTRAN system, Level 1, is implemented by the Physical Layer (“PHY”) in the UE and in the e-Node B and the PHY performs the physical transport of the packets between them over the air interface using radio frequency signals. In order to ensure a transmitted packet was received, an automatic retransmit request (“ARQ”) and a hybrid automatic retransmit request (“HARQ”) approach are provided. Thus, whenever the UE receives packets through one of several downlink channels, including common channels and shared channels, the UE performs a communications error check on the received packets, typically a Cyclic Redundancy Check (CRC), and in a later subframe following the reception of the packets, transmits a response on the uplink to the e-Node B or base station. The response is either an Acknowledgement (ACK) or a Negative Acknowledgement (NACK) message. If the response is a NACK, the e-Node B automatically retransmits the packets in a later subframe on the downlink or DL. In the same manner, any UL transmission from the UE to the e-Node B is responded to, later in time, by a NACK/ACK message on the DL channel to complete the HARQ. In this manner, the packet communications system remains robust with a low latency time and fast turnaround time.
As presently proposed, uplink HARQ messages are synchronous. The synchronous HARQ follows a downlink transmission from an eNB to a UE by a predetermined number of subframes. The use of the synchronous HARQ therefore places timing requirements on the following subframes, as an uplink HARQ message must be able to be transmitted within certain time constraints.
E-UTRAN networks may provide support for various traffic types. UEs may include, as non-limiting examples, web based wireless appliances such as web browsing devices. Internet based video delivery may be provided, for mobile television or audio or video program delivery. Some of these applications are very asymmetric in terms of data volume in UL and DL direction; often downlink traffic to the UE will be far more frequent than uplink traffic from the UE. As the user interfaces with the UE device, the traffic allocation may change. For example, the user may send email, make voice calls, or access other services and then later return to web browsing. Ideally, the UE and the eNB could dynamically allocate the subframes to provide more data capacity in one direction, or the other.
The e-UTRAN project requires backwards compatibility support as well. To provide this support, any changes to the interface timing must also be compatible with devices that do not implement the improvements. For example, currently, so called “Release 8” devices are being contemplated. If these devices are produced, any changes to the e-UTRAN timing specifications must be implemented in such a manner so that these earlier devices will still operate correctly in the system, even though later devices may have additional features.
A continuing need thus exists for a system, methods and circuitry to implement support for certain dynamic changes to the subframe allocations between an eNB and a UE to provide better support for asymmetric data traffic, when appropriate.